To pull tightly on the skin around one testicle and squeeze that testicle up, isolating it. The resulting isolation of one testicle takes on the conspicuous form of a mushroom cloud after an atomic bomb explosion. Performing this trick with both testicles results in the popular "The Brain."

Louis was walking and turned when Carl called his name to see Carl giving him The Atomic Bomb, and he had nightmares about that hellish, veiny testicle mushroom cloud for weeks.